I have had very good luck with Classic Parts. Just be aware, you usually get what you pay for. The trans mount repair kit for $7 is just some rubber and a couple of bolts. The more expensive mounts have the rubber bonded to the steel pieces. The cheap repair kit isn't going to provide much cushioning effect at all. On the other hand many people say you don't need the mount at all. I choose the cheap repair route myself.
Chuck